What is the probability of selecting a prime number from 1,2,3,........10 ?
- 17
- 21
- 23
- 25
Ans. [4]
Small stuff of Mathematics
Q 1: 123456 *999 =?
Sol.
123456*999
123456000
- 123456
123332544
Description: it apply only in case of multiply with 999999…….at first step put zeros according to digit 9(in this example three 9, so put three zero)and the all numbers the subtract all numbers and you will get the answer.
Q 2: (11)2
Ans 121
Q 3: (111)2
Ans 12321
Q 4: (1111)2
Ans 1234321
Q 5: (11111)2
Ans 123454321
Description: it apply only in the square of series of 1, simply count the 1, write from left up to last number(ex. Q5. There five 1 so write 12345) and then write in descending order (4321) hence the answer
Square TRICK
Square of double-digit numbers: [ example= (99)2 = ? ]
Note: it is applied only 11 to 99
Trick: [AB]2 = [A]2 [2*A*B] [B]2
It is very easy, try to do only two question on notebook and really it is very useful
Ex. 1. (56)2 = ?
=[5]2 [2*5*6] [6]2
= [6] {6 square = 36, but we will take only 6 and carry 3 to add}
= [60+(3)] [6] { 2*5*6=60 + 3(carried number) = 63, put only 3 and carry 6}
= [3] [6]
= [25+6] [3] [6] {25+6= 31}
= [31] [3] [6] {now right all digit continuously)
= 3136 Ans.
Q.2. (63)2 = ?
= 9
= 69
= 3969 Hence
Q.2 (84)2 = ?
= 6
= 56
= 7056 Ans.
Q.3. (93)2 = ?
= 9
= 49
= 8649 Ans.
